Electronic calculators have become a common tool for teaching students various phases of mathematics. In particular, the features of graphing calculators result in their use in the classroom as providing significant advantages. Graphing calculators are characterized by a large screen, which permits the entry of mathematic expressions in traditional format and also allows multi-lines of information. These graphing calculators also permit displays of graphs, display of tables and rather complex programming. Preferred graphing calculators also permit data transmission to other computing devices, directly or by means of a data storage medium as well as data collection by means of various interface protocols. Many calculator models are designed for particular education levels, however, regardless of the level for which a calculator is designed, a usual goal is to provide a logical and easy to use interface with the student. Two commercially available calculators which are particularly suitable as teaching tools are the “TI-89” and “TI-92 Plus” Graphing Calculators available from Texas Instruments Incorporated of Dallas, Tex.